William R. Walsh wrote:
Hello all...
Let me start by saying that these are no ordinary computer power supplies.
They are Delta 335 watt supplies that come from IBM PS/2 Servers. They are
rather complicated inside. This is a long post, but please bear with me.
The mode of failure is that the supply just plain quits...mine have either
died silently while running or have not come back on after power failures.
There are no signs of distress in these supplies--they just quit running out
of the blue.
As a PS/2 collector and hobbyist who keeps his PS/2s in regular use, I find
this failure very troubling. These supplies are solidly built...it is hard
to imagine them just silently dying, but that is what happens. Conversation
with others who have these systems have revealed that this is not something
happening only to me.
I am desperately seeking assistance in troubleshooting these supplies. I
don't have the skills or comfort level to diagnose them. What I'm looking
for is someone who would be willing to have a look at these supplies and at
least provide a reason for their failure. If they can be fixed--that's
great--but it is not the primary goal. I want to know *why* they died.
Sam Goldwasser (whom I sincerely hope does not mind my mentioning his name)
looked at one of the supplies and was able to find out some information--if
my understanding is correct, he found that the standby supply was working
but the TL494 controller was being told to shut down with the "dead time
control" pin 4.
I'd really appreciate any help with these supplies. I'm desperate for help
and running out of places to look. I am more than willing to pay for your
time and shipping of the supply both ways.
If you can help, please post back here to the group or send an e-mail to:
wct atsign walshcomptech dot com. Thank you.
William
Well, it would take a fair amount of time to do it right.
If i were to guess, bad solder joints and capacitors are
the primary suspects. The bad solder joints are pretty
straight forward if you know what to look for.
The caps would take a ESR meter at minimum to check for
series resistance. This might involve taking them out of
circuit in some cases.
If one was going deep into this, you would have to reverse
engineer a schematic along with data sheets to figure out
what's really going on inside. And that's highly time
consuming. You got the funds to to that?
There is always the possibility that there is some latent failure
of the power transformers or such. Those parts will NOT be
readily available if they can be found at all. A 494 is a pretty
common switcher control IC. Used commonly in car stereo amps.
Bob
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